| Regional Biophysics Meeting 2005, March 16-20, Zreče, Slovenia | [MembBiophys] |
Earlier we have shown that the macrodomain organization of the main chlorophyll a/b light harvesting complex, LHCII, of photosystem II in thylakoid membranes plays a key role in stabilizing the granal ultrastructure of chloroplast thylakoid membranes (Mustárdy and Garab, 2003 Trends Plant Sci.). These macrodomains have also been shown to possess an unexpected structural flexibility: they are capable of undergoing light-induced reversible structural reorganizations that are largely independent of the photochemical activity of thylakoids and are linearly proportional to the light intensity above the saturation of photosynthesis – a unique feature with respect to the adaptation and protection of plants against excess excitation. This structural flexibility has been shown to be driven by a novel, biological thermo-optic mechanism. Fast thermal transients arising from dissipated excitation energy can lead to elementary structural transitions because of the existence of ‘built-in’ thermal instabilities in the close vicinity (<2 nm) of the sites of dissipation (Cseh et al. 2000 Biochemistry; Garab et al 2002 Biochemistry). We have identified several well discernible thermo-optically induced structural changes in LHCII-containing and cyanobacterial antennae (Dobrikova et al. 2003 Biochemistry; O. Zsiros, K. Stoichkova,T. Jávorfi, Z. Gombos, A. Andreeva, T. Páli and G. Garab, in preparation). In granal thylakoids the reorganziations are accompanied (or triggered) by changes in the lipid phase behavior (S. Krumova, C. Dijkema, G. Garab and H. van Amerongen, in preparation), due to the non-bilayer propensity of the thylakoid lipids, and are in line with the hypothesis (Garab et al. 2000 Trends Plant Sci.) that non-bilayer lipids contribute significantly to the structural dynamics of biological membranes.
Email: gyozo@brc.hu
Address: Gyozo Garab,, BRC, POB 521 H-6701 Szeged Hungary